Merge pull request #38 from tomtom-international/feature/slf4j

feat: in quiet mode dont log sl4j errors during james initialization

james-agent/src/main/java/com/tomtom/james/newagent/JVMAgent.java

@@ -108,8 +108,10 @@ private static void setupAgent(Instrumentation inst) {
             Logger.setCurrentLogLevel(configuration.getLogLevel());
             printBanner(configuration);
 
-            Stopwatch stopwatch = Stopwatch.createStarted();
+            if (configuration.isQuiet())
+                SystemErrCapture.register();
 
+            Stopwatch stopwatch = Stopwatch.createStarted();
             PluginManager pluginManager = new PluginManager(configuration.getPluginIncludeDirectories(), configuration.getPluginIncludeFiles());
             LOG.trace("pluginManager time=" + stopwatch.elapsed());
 
@@ -181,6 +183,8 @@ private static void setupAgent(Instrumentation inst) {
 
         } catch (ConfigurationInitializationException e) {
             e.printStackTrace();
+        } finally {
+            SystemErrCapture.unregisterAndReplay(line -> !line.startsWith("SLF4J:"));
         }
     }
 

james-agent/src/main/java/com/tomtom/james/newagent/SystemErrCapture.java

@@ -0,0 +1,46 @@
+package com.tomtom.james.newagent;
+
+import com.google.common.io.CharStreams;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.io.StringReader;
+import java.util.function.Predicate;
+
+public class SystemErrCapture {
+
+    private static PrintStream oldErrStream;
+    private static ByteArrayOutputStream outputStream;
+    private static PrintStream newErrStream;
+
+    public static void register() {
+        SystemErrCapture.oldErrStream = System.err;
+        outputStream = new ByteArrayOutputStream();
+        newErrStream = new PrintStream(outputStream);
+        System.setErr(newErrStream);
+    }
+
+    public static void unregisterAndReplay(Predicate<String> predicate) {
+        if (newErrStream == null) {
+            return;
+        }
+        newErrStream.close();
+        System.setErr(oldErrStream);
+
+        replayErrorsMatchingPredicate(outputStream, predicate);
+        newErrStream = null;
+        outputStream = null;
+    }
+
+
+    private static void replayErrorsMatchingPredicate(final ByteArrayOutputStream outputStream,
+                                                final Predicate<String> predicate) {
+        try {
+            CharStreams.readLines(new StringReader(outputStream.toString()))
+                       .stream().filter(predicate::test)
+                       .forEach(System.err::println);
+        } catch (IOException e) {
+            // ignore me
+        }
+    }
+}